1. Field of the Invention
The present invention relates to multi-type air conditioners, and more particularly, to a method for controlling a multi-type air conditioner for preventing damage to a compressor.
2. Discussion of the Related Art
In general, the air conditioner cools or/and heats rooms as the air conditioner performs steps of compression, condensing, expansion, and evaporation of refrigerant. In air conditioning systems, there are cooling air conditioner for supplying cold air to the room by operating a refrigerating cycle only in one direction, and cooling/heating air conditioner for supplying cold or warm air to the room by operating the refrigerating cycle in either direction, selectively. Moreover, there are general air conditioners in which one indoor unit is connected to one outdoor unit, and multi-type air conditioners in which a plurality of indoor units are connected to one outdoor unit. In the meantime, the multi-type air conditioner may have one of more than one outdoor unit.
The multi-type air conditioner integrates operating time periods, and determines if the integrated time period reaches to an integrated time period preset at a control unit. If it is determined that the integrated time period reached to the integrated time period, an oil recovery operation is performed in which an expansion device in the indoor unit is opened, and the compressor is driven at the highest rotation frequency, for recovering oil accumulated in the indoor unit.
In the meantime, the multi-type air conditioner employs an individual power source system in which a plug for an indoor unit is plugged in/out at the room, individually. The air conditioner of such an individual power source system can be turned off as a user plugs-out.
However, the air conditioner of the individual power source system has the following problems.
First, if most of the users plugged-out the indoor units, even if the outdoor unit tries to access to the indoor units with communication, only to fail. In this instance, because the control unit of the outdoor unit can not open the expansion devices of the indoor units access to which have failed, after opening the expansion devices of the indoor units access to which were successive fully, the oil recovery operation is performed. Therefore, since refrigerant can not be recovered from the indoor units access to which have failed, while recovering the refrigerant from the indoor units access to which were successive merely, a refrigerant recovery ratio can not but become poor, substantially.
Second, since the compressor rotates at a high speed at the time of the refrigerant recovery operation, the more a number of the indoor units access to which have failed, a rate of oil discharged from the compressor becomes relatively greater than a rate of oil recovered to the compressor. Therefore, in a state a number of indoor units access to which have failed is greater than a number of units access to which were successive, the more the refrigerant recovery operation is made, the more amount of oil is reduced from the compressor, gradually.
Third, as above, there are cases when an adequate amount of oil for operating the compressor can not be recovered even if the refrigerant recovery operation is made thus, when the compressor is liable to damage if the compressor is kept operated in such a state.
Fourth, since the compressor is operative even in a state of oil shortage, the related art multi-type air conditioner can not know the damage to the compressor in advance, or deal with the damage to the compressor with flexibility.